This application relates to fall arrest units, and, in particular to sealed component fall arrest units in which all the rotating components (i.e., return spring, drum, and clutch) are supported by a cantilevered main shaft or spindle rotatably mounted in the housing of the fall arrest unit so as to prevent the housing itself from bearing any substantial load. Further, the construction of the fall arrest unit allows for the entire working assembly to be easily accessed to facilitate replacement of worn, damaged, or non-functioning parts.
Retractable fall arrestors or lifelines have been used for many years and range in size from small (6 ft.) units to large (175 ft.) units. The purpose of a retractable lifeline or fall arrest unit is to allow workers, who must work on the leading edge of elevated surfaces (or other areas where falls are of concern) to have a means to attach to an anchorage that will arrest their motion in case of an accidental fall. These retractables are usually equipped with a 3/16″ wire rope cable or a 1″ webbing lanyard, currently, of at least 3600 lbs. of anchorage strength. The retractables are equipped with shock absorbers that will limit the forces of a falling worker to 900 lbs. or less during a fall arrest. These shock absorbers may comprise an internal mechanical clutch type or an external rip-stop type made of webbing. The internal clutch mechanisms usually comprise a stack of friction disks which are held under a known compressive force by preloaded Belleville springs. The internal clutch mechanism normally is activated by a centrifugal pawl mechanism only after the falling worker achieves a certain velocity. The advantage of a mechanical clutch type shock absorber over a webbing rip-stop type shock absorber is that the internal clutch mechanism will activate much more quickly with less free fall than the webbing rip-stop type shock absorber. The shorter free fall reduces input energy and generates a lower fall arrest force.
One of the difficulties of using mechanical retractable shock absorbing lifelines is that they must be periodically inspected for damage and be retested to confirm that they are operating correctly. This is usually done yearly and requires each fall arrest unit to be returned to the manufacturer for recertification. The reason these units must be returned to the manufacturer is because they are mechanically difficult to service due to the precision setting required on the clutch assembly and the difficulty of unloading and removing the power retraction springs, which may be over 100 ft. long. This is both costly and time consuming, requiring the customer to purchase extra units that can be rotated out of service for recertification on a regular schedule.
These problems are greatly compounded when retractable units are used in off-shore work sites where the retractables will be exposed to a salt (and thus, corrosive) atmosphere. In such conditions, the retractable must be serviced and recertified after approximately four months. Further, when a retractable is being serviced, it is out of commission for about two months.